The present invention relates to a process for preparing tris[(1H,1H,2H,2H-perfluroalkyl)aryl] phosphites, referred to hereinbelow as fluorine-containing aryl phosphites.
The present invention also relates to the said fluorine-containing aryl phosphites and to their uses in particular in two-phase catalysis with a fluorine-containing phase.
This two-phase catalysis with a fluorine-containing phase has been described by Istvan T. Horwath et al. in patent U.S. Pat. No. 5,463,082.
The general concept of this catalysis is based on the use of a fluorinated phase which is immiscible with an organic phase without heating and generally miscible when heated.
The fluorinated phase is a solvent rich in C-F bonds (fluorocarbons or hydrofluorocarbons).
When not heated, the system consists of two phases:
a fluorinated phase which is a solvent rich in C-F bonds and which contains a catalyst made soluble in said fluorine-containing solvent by means of fluorine-containing chains,
a hydrocarbon-based organic phase, which is immiscible with the fluorine-containing phase, and which contains the reagents.
The catalysis reaction is carried out with heating in a phase which is generally homogeneous, that is to say that above a certain temperature a single phase is generally obtained in which the catalysis takes place. Once the reaction is complete, the catalysis is readily recovered by cooling the reaction medium to a temperature below the temperature of miscibility of the two phases.
Thus, in order to make the catalyst preferentially soluble in the fluorine-containing phase, it has been recommended to functionalize it with one or more perfluoroalkyl groups.
The perfluoroalkyl groups of the fluorine-containing phosphites used as coordination ligands have electron-withdrawing properties which may influence the coordination characteristics of the phosphorus atom and thus adversely modify the catalytic activity of the catalysts made with such fluorine-containing ligands.
In order to reduce these adverse effects of the perfluoroalkyl chains on the phosphorus atom, it has been proposed to introduce non-fluorine-containing groups known as xe2x80x9cspacersxe2x80x9d between the phosphorus atom and said perfluoroalkyl chain.
Examples of such spacers which may be mentioned are polymethylene radicals (CH2)n with n ranging from 1 to 3 and the phenylene radical xe2x80x94C6H4xe2x80x94.
As illustrations of fluorine-containing phosphites containing such spacers, mention will be made of tris (1H,1H,1H,2H,2H-perfluoroalkyl) phosphite mentioned by I. T. Horwath et al. in patent U.S. Pat. No. 5,463,082; tris(4-tridecafluorohexylphenyl) phosphite mentioned by E. G. Hope et al. in J. Chem. Soc. Perkin Trans. 1. 1997, pages 3609-3612, and the tris(perfluoroalkylphenyl) phosphites mentioned by T. Mathivet et al. in Tetrahedron Letters 39, 1998, pages 9411-9414.
In general, these fluorine-containing phosphites are obtained with low yields, by processes using expensive reagents and with long reaction times (several days) in particular, for the aryl phosphites containing perfluoroalkyl chains.
Thus, for example, E. G. Hope et al. (J. Chem. Soc. Perkin Trans. 1, 1997, pages 3609-3612) obtain tris(4-tridecafluorohexylphenyl) phosphite by synthesizing, in a first step, 4-tridecafluorophenol by reacting C6F13I dissolved in hexafluorobenzene with para-iodophenol in the presence of copper in DMSO at 80xc2x0 C., under nitrogen for 6 days. In a second step, the 4-tridecafluorophenol, obtained in a yield of 63%, is introduced slowly with triethylamine into a solution of PCl3 in Et2O. The tris(4-tridecafluorohexylphenyl) phosphite is obtained in a yield of 55.7%, ie an overall yield of 35%.
Mathivet et al. (Tetrahedron Letters, 39, 1998, pages 9411-9414) also use the reaction of a perfluoroalkyl iodide with bromophenol or iodophenol to obtain the (perfluoroalkyl)phenols, but they perform the process in DMSO. They obtain the (perfluoroalkyl)phenols in yields ranging from 23% for 2-methyl-4-perfluorooctylphenol to 70% for 4-perfluorooctylphenol.
The use of the reaction between an iodophenol or bromophenol and an iodoqerfluoroalkyl in the presence of copper (Ullmann reaction) does not allow 1H,1H,2H,2H-perfluoroalkyl groups to be introduced onto the phenol nucleus.
Japanese patent application JP 7-179 384 describes the production of 4-(1H,1H,2H,2H-perfluoroalkyl)phenol by carrying but the following reactions:
reaction of an alcohol CF3(CH2)pCH2CH2OH with triflic acid to give an ester of formula: CF3(CH2)pCH2CH2OSO2CF3 (with p=1 to 15),
followed by reaction of said ester with a Grignard reagent obtained from magnesium and a p-alkoxyhalobenzene to give the 4-(1H,1H,2H,2H-perfluoroalkyl)-alkoxybenzene and, after cleavage of the alkoxy function, to give the 4-(1H,1H,2H,2H-perfluoroalkyl)-phenol in yields in the region of 50%.
However, performing the process in this way has the drawback of using expensive reagents: the alcohols CF3(CF2)pCH2CH2OH and triflic acid, the latter also being difficult to handle.
A process has now been found for preparing tris[(1H,1H,2H,2H-perfluoroalkyl)phenyl] phosphites of formula (I): 
in which the (5-x)R, which may be identical or different, represent a hydrogen atom, a linear or branched alkyl radical containing a number of carbon atoms ranging from 1 to 10; a halogen atom such as bromine or chlorine; Rf represents a 1H,1H,2H,2H-perfluoroalkyl radical CnF2n+1C2H4xe2x80x94 with n ranging from 4 to 20 and preferably ranging from 8 to 20, x is an integer ranging from 1 to 5 and preferably ranging from 1 to 3; characterized in that it comprises the steps consisting in:
a) preparing a Grignard reagent of formula (II) 
xe2x80x83from an alkoxyhalobenzene of formula (III): 
xe2x80x83in which formulae R1 represents a linear or branched alkyl radical containing a number of carbon atoms ranging from 1 to 6 and preferably ranging from 1 to 3, X represents a bromine, chlorine or iodine atom, R and x having the same meanings as in formula (I), followed by reacting said compound (II) with a 1-iodo-1H,1H,2H,2H-perfluoroalkane CnF2n+1C2H4I (IV), represented hereinbelow by RfI, to give a (1H,1H,2H,2H-perfluoroalkyl)alkoxybenzene (V): 
c) converting the alkoxy function R1Oxe2x80x94 of (V) obtained in step a) into a hydroxyl function HOxe2x88x92 to give a (1H,1H,2H,2H-perfluoroalkyl)hydroxybenzene of formula (VI): 
d) reacting compound (VI) obtained in step b) with PCl3 to give the tris[(1H,1H,2H,2H-perfluoroalkyl)phenyl] phosphite (I).
The Grignard reagent (II) is obtained according to methods known to those skilled in the art, which consist in reacting an alkoxyhalobenzene of formula (III) with magnesium in an ethereal solvent such as diethyl ether or THF at room temperature.
Preferably, X represents a bromine atom.
As illustrations of bromoalkoxybenzenes which may be used according to the present invention, mention will be made of 4-bromoanisole, 3-bromoanisole, 2,4-dibromoanisole, 2,4,6-tribromoanisole, 4-bromo-2,6-dimethylanisole and 4-bromophenetole.
The reaction between the Grignard reagent (II) and the iodofluoro compound RfI is carried out in the presence of copper iodide CuI used in weight amounts ranging from 0.1% to 10% relative to the compound RfI.
Preferably, the ethereal solution of the Grignard reagent is introduced slowly into an ethereal suspension of RfI plus CuI at a temperature in the region of 0xc2x0 C. and, once the addition is complete, the reaction medium is then maintained at 20-30xc2x0 C. with stirring for a period of not more than 6 hours and preferably between 1 and 3 hours.
Then, the medium is hydrolyzed and the compound (V) is isolated according to methods known to those skilled in the art (extraction, washing, drying and removal of the solvent under reduced pressure).
As illustrations of RfI which may be used according to the present invention, mention will be made of 1-iodo-1H,1H,2H,2H-perfluorodecane CF3(CH2)7CH2CH2I and 1-iodo-1H,1H,2H,2H-perfluorooctane CF3(CH2)5CH2CH2I.
The cleavage of the alkoxy function R1O in compound (V), step b) is carried out by methods known to those skilled in the art, in particular using boron tribromide BBr3 in an organic solvent such as benzene or toluene at a temperature of between 60xc2x0 C. and 100xc2x0 C. and preferably between 70xc2x0 C. and 90xc2x0 C.
The reaction medium obtained is then cooled, after which it is introduced into water. The hydroxylated compound (VI) is isolated in a known manner.
According to the process of the present invention, BBr3 is used in a molar ratio: compound (V)/BBr3 of between 1 and 1.5 and preferably between 1.2 and 1.4.
The reaction between compound (VI) and PCl3, step c), is carried out in an organic solvent such as THF or diethyl ether Et2O, in the presence of a tertiary base such as pyridine or triethylamine.
The process is performed at low temperature, xe2x88x9210xc2x0 C. to 0xc2x0 C., by introducing PCl3 into a medium containing an organic solvent, the tertiary base and the fluorophenol compound (VI).
Once the addition is complete, the reaction medium is allowed to return to a temperature of about +20xc2x0 C. to +30xc2x0 C. and the medium is then maintained at this temperature with vigorous stirring for several hours. Next, the mixture is filtered and the fluorine-containing aryl phosphite (I) is isolated from the filtrate by removing the organic solvent under reduced pressure.
The compounds obtained in steps a), b) and c) may be identified by elemental analysis, proton, 19F, 13C and 31P NMR and by mass spectrometry (MS).
The process according to the present invention has the advantage of obtaining fluorine-containing aryl phosphites (I) in good yields from commercially available reagents.
Another subject of the invention concerns tris[(1H,1H,2H,2H-perfluoroalkyl)phenyl] phosphites of formula (I) described above.
Among the compounds of formula (I) that are preferred are those in which x=1, 2 or 3, R=H or CH3xe2x80x94 and Rf=CH3(CF2)7C2H4xe2x80x94.
As representatives of such compounds, mention will be made most particularly of
tris[4-(1H,1H,2H,2H-perfluorodecyl)phenyl] phosphate,
tris[2-(1H,1H,2H,2H-perfluorodecyl)phenyl] phosphite,
tris[2,4-bis(1H,1H,2H,2H-perfluorodecyl)phenyl] phosphite,
or tris[3-(1H,1H,2H,2H-perfluoroalkyl)-5-chlorophenyl] phosphite,
which are particularly preferred and whose manufacturing process and spectroscopic characteristics are detailed in Examples 1 to 4 below.
The fluorine-containing aryl phosphites (I) are resistant to hydrolysis and highly soluble in perfluorinated solvents, which allows them to be used advantageously as transition metal ligands for preparing catalysts which may be used in particular in two-phase catalysis with a fluorine-containing phase to carry out chemical reactions of hydroformylation, of hydrogenation of unsaturated compounds, of carbonylation, telomerization and cyclodimerization of dienes, and of hydrocyanation of olefins or conjugated dienes.
Another subject of the invention is thus the use of the tris[(1H,1H,2H,2H-perfluoroalkyl)phenyl] phosphites of formula (I) as transition metal ligands for the preparation of catalysts for the abovementioned chemical reactions.
As examples of transition metals which may be used according to the present invention, mention will be made of rhodium, palladium, ruthenium, nickel, iridium, chromium, cobalt and iron.
The catalysts obtained with the fluorine-containing phosphites (I) of the present invention used as ligands have the advantage of being readily separated out and recycled when they are used in fluorine-containing two-phase catalysis.
In addition, the Applicant has found that, during the hydroformylation reaction of olefins, and in particular during the hydroformylation of 1-decene with a catalyst of the rhodium type complexed with tris[4-(1H,1H,2H,2H-perfluorodecyl)phenyl) phosphite, said catalyst can be recycled without any loss of catalytic activity.
The catalyst according to the present invention may be prepared in situ, that is to say in the reactor in which the chemical reaction is carried out, by mixing the transition metal, generally in the form of a metal complex or a metal salt, with the compounds of formula (I) obtained according to the process of the present invention, or alternatively may be prepared and isolated separately.